Coarse-grayed aggregates with a size of 20 mm or less are commonly used for most concrete constructions. The texture of the surface, the shape of the particles and the cleanliness of the coarse-grained aggregate can be roughly checked only by visual observation. However, porosity and gradations require specific laboratory testing.
Concrete aggregatesare produced to Australian standards (AS 275) or to more specific customer requirements.
Coarse-grayed aggregates with 20 mm and smaller sizes are commonly used for most concrete constructions. The ideal construction aggregate should have a rough surface texture and must be clean, strong and free of coating and other dirt particles. Keep in mind that the size of the aggregates is the size that most parts pass through a sieve of that size, not all, so there is no need to be too demanding. To obtain the same strength or workability, concrete with large aggregate will require a smaller amount of cement than concrete with a smaller aggregate.
But in practice, the size of the aggregate cannot be increased to any limit due to limitations in mixing, handling and placing equipment. In your contract, construction or purchase agreement, the term “maximum aggregate size” refers to the smallest sieve that 100% of your aggregate can pass through. In general, you'll want smaller coarse-grated aggregates for stronger concrete, with 20mm aggregates meeting the threshold for strong concrete and 40mm aggregates for normal strength concrete. If you are looking for medium strength concrete, get 40mm aggregates, but if you are looking for high strength, 20mm is best.
It can be a single size material, typically 20 mm, 14 mm, 10 mm, or 7 mm, or a graded aggregate consisting of a single size aggregate mixture. In a mass concrete job, the use of larger aggregates will be useful due to the lower cement consumption. Aggregates are a broad category of materials, such as sand, gravel, crushed stone, slag, and recycled concrete. The selection of good quality coarse-grated aggregates is essential for the production of concrete that meets the desired strength and durability requirements.
In large aggregates, the surface area to be wetted per unit weight is smaller, and the water-cement ratio is lower, which increases strength.